1. Field of the Invention
The present invention is more particularly applicable to a conventional cooling system for an internal combustion engine, comprising especially:
a pump for water or other cooling liquid, having a mechanical drive; PA1 a fan having an electrical or directly mechanical or declutchable drive; PA1 a radiator equipped with a cap which may or may not be calibrated; and PA1 an expansion-tank equipped with a cap which may or may not be calibrated. PA1 the time constant; PA1 the energy relating to the thermal inertia of the engine.
2. Description of the Prior Art
In the motorcar industry it has already been proposed a very long time ago to have the expansion of the cooling liquid of the engine absorbed by an expansion-tank, as in current fixed heating installations. The French Pat. No. 1.269.341 of the 2nd of July 1960 describes such a radiator system associated with an expansion-tank.
Sometimes with such a conventional system, violent overheating is found after the engine has operated at full load for a long time, for example, while running along a motorway or while climbing a long hill slope, one stops for some reason or other (toll-house, customs, rest area), because of the reduction in ventilation. Experience proves that the return from running at full load to slow running is accompanied by supplementary energy which must be removed, as compared with stabilized slow running. This phenomenon is known by the name of "thermal inertia" of the engine. It is characterized by two main parameters:
This energy is of the order of 60 to 90 kcal (for an engine of 7 to 10 HP) and hence might heat 1 kg of water from 0.degree. C. up to 60.degree. to 90.degree. C. From the standpoint of the energy, the thermal inertia does not present any importance; on the contrary, from the standpoint of the power, because of the time constant, it represents up to the order of magnitude of the power of the radiator in stabilized slow running (about 5000 kcal/h).
However, for a conventional cooling circuit assembly as above, slightly under-dimensioned or correctly dimensioned with respect to stabilized slow running, the thermal inertia of the engine at the time of passing from full load running to unexpected slow running, brings about a rise in the temperature of the cooling liquid of the engine. This rise lasts for a long time and may reach the boiling point, which causes disastrous consequences.